1. Technical Field
The present disclosure relates to a workpiece cloth ruler detachably attachable to an attaching part of a cloth presser holder or a walking foot so that workpiece cloth such as quilting cloth is sewn while a stitch line interval is held constant.
2. Description of the Related Art
Quilting rulers (workpiece cloth rulers) are generally used when stitches are sewn so as to be spaced away from a previous stitch line in the case where quilting stitches are carried out in which, for example, stitches are formed lengthwise and crosswise on quilting cloth. A quilting ruler is detachably attached to an attached part of a cloth presser holder or a walking foot attached to a lower end of a presser bar, as occasion arises. Various types of quilting rulers have been proposed and put into practical use. For example, JP-Y-S53-52500 (first reference) discloses a ruler bar holder in which a recess is formed in an upper part of a rear support of a presser holder. A ruler bar includes a horizontal part fitted in the recess so as to be pressed against the recess by a leaf spring. In this construction, the horizontal part of the ruler bar has a section formed into the shape of a drum. The leaf spring has a free end which is usually pressed against a flat surface of the drum-shaped horizontal part, whereupon the ruler bar is retained at a predetermined position with respect to a horizontal direction thereof.
Furthermore, JP-U1-H05-70477 (second reference) discloses a ruler bar holder comprising a cover having two opposed walls formed with respective U-shaped grooves. Each groove has one end which is open outwards. The ruler bar bent into an L-shape has a shaft having a circular section and thrust into a recess of the U-shaped groove of the cover, whereby the ruler bar is retained between the recess and protrusion.
In the ruler bar holder disclosed in the first reference, the horizontal part of the ruler bar having the section formed into the drum-shape is pressed against the recess of the rear support by the spring force of the leaf spring. Furthermore, in the ruler bar holder disclosed by the second reference, the ruler bar is adapted to be retained at a predetermined initially mounted position by the holding force of the recess of each U-shaped groove. Accordingly, particularly when quilting cloth is to be sewn, the ruler bar of each above-noted reference passes an upwardly corrugated swollen part of the surface of the quilting cloth and is thereafter held in an upwardly lifted state. More specifically, when once lifted up, the ruler bar is not lowered by the self-weight but held in the lifted state since the spring force of the leaf spring or the holding force is strong. Since the ruler bar is not effective as a gauge in this state, the operator needs to lower the ruler bar manually so that the ruler bar contacts the surface of the quilting cloth, whereupon the working efficiency in quilting is lowered.
In view of the aforesaid problem, it is considered that an upwardly elastically deformable spring steel or spring wire is used to constitute a one-end guide located at one side of the presser foot in the ruler bar or a forward directed ruling part of the ruler bar. However, when the guide or ruling part is made of spring steel, the thickness of the spring steel needs to be increased so as to be prevented from plastic deformation even in subjection to an unexpected external force. Furthermore, the width of the spring steel needs to be increased so that a suitable strength is obtained. When the guide or ruling part is made of spring wire, wire diameter needs to be increased so that a suitable strength is achieved. As a result, the spring constant is increased and accordingly, an amount of change in the spring force is increased relative to the flexible volume of the spring. Particularly in quilting, the ruler bar cannot be moved smoothly along the corrugated surface of the quilting cloth.